Earth boring rock bit



INVENTOR x 27" lo Nov. 14, 1944. RQSSMAN EARTH BORING ROCK BIT Filed D90. 22, 1941 v v 3 J.

BY Auk/7M 055mm? 3 z am Patented Nov. 14, 1944 UNITED STATES PATENT OFFICE aaa'rn BORING aoox BIT Allen M. Rossman, Wilmette, Ill.

Application December 22, 1941, Serial No. 423,979

7 Claim.

This invention relates to drill bits, more particularly to rock drill bits used in earth boring which is so constructed that the wear on the bearing is less than the normal wear on the drilling surface of the bit so that the bearing will not be responsible for requiring raising of the drill pipe and bit for replacement purposes.

The cutting member of the bit of the present invention is a single cone, the apexof which is coincident with the center of the drilled hole and which cone has teeth formed on theconical surface thereof. The central axis of the cone is mounted at a fixed inclination with the central vertical axis of the drilled hole.

The drilling cone or bit carries a central stem which extends upwardly for connection with a drill pipe. It may project into the drill pipe, or the drill pipe may project into the extension. The two are connected together so that when the pipe is rotated the central axis of the stem is rotated around the central axis of the drilled hole as a unit with the drill pipe. At the same time the cutting face of the drill rolls on the bottom of the hole with a true rolling motion. The circumference of the edge of the hole drilled by the bit is greater than the circumference of the edge of the bit so that each revolution of the drill pipe brings each cutting tooth of the drill in contact with a point on the surface of the bottom of the hole a short distance back 'of the poiht'int'o which the cutting tooth cut on the preceding revolution. The motion of the drill on the bottom of the hole is a true rolling motion without sliding action.

Thrust roller bearings between the cone and the drill pipe carry the thrust pressure of the drill pipe and keep the stem of the cone axially centered. The bearings are packed in lubricant and closed by sealing rings. It is a further object of the present invention to provide an arrangement such that there is no pressure difierence on the outer sides of the different sealing rings or gaskets that seal the bearing. Thus there is no tendency for external fluids, such as, for instance, the mud circulated during'the drilling operations, to creep past a sealing ring into the bearing.

It is a further object of the present invention to provide a bit with means for guiding it in the bore drilled thereby. In the specific embodiment of the invention here illustrated this means comprises a lip which encircles the cone and which is perpendicular to a radial line of the conical surface at the point of intersection of each radial line with the lip. The lip thus serves a number of useful purposes. ing one of the raceways of the thrust bearing and it provides a bearing surface against the side wall of the well to resist the side-thrust of the force that results from the eccentric thrust on the bit.

The attainment of the above and further objects of the present invention will be apparent from the following specification taken in conjunction with the accompanying drawing forming a part thereof.

In the drawing:

Figure 1 is a longitudinal section of a rotary I bit and bearing assembly incorporating the fea- .at an inclination to the vertical axis 2;

tures of the present inventiom'and Figure 2 is a sectional view taken along the line 2-4 of Figure 1 and looking in the direction of the arrows,

Reference may now be had more particularly to the drawing in which like reference numerals indicate like parts.

A vertical drill pipe I, which is axially rotatable about its central axis 2, has an offset body or fitting threaded on or otherwise suitably secured to the bottom thereof. The fitting 3 terminates in a cylindrical portion 4 having its central axis 5 The cylindrical portion 4 has an internal circular shoulder I which has a central opening through which the stem of the cutting bit extends, in a manner to be more fully explained as this description proceeds.

A drill bit It is iournalled in the cylindrical portion 4 of the body 3. The drill bit has a plurality of cutting or chipping teeth II on a conical surface, the cutting teeth being of any desired shape and formation, as is well known in the art. Certain of the teeth extend from the outer periphery to the center or apex of the cone It provides a surface for holdouter surface I4 perpendicular at all radial lines of the hypothetical conical surface about which the teeth II are formed. The outer surface I4 is thus also a cone, one element of which extends vertically and is in contact with the wall of the hole being drilled. The bit has a hollow cylindrical stem I6 which is an integral part thereof and extends into the cylindrical portion 4 of the fitting 3 and is centered about the axis 5. The axis 6 is also the axis of the cone I4, and each radial element of the cone I4 makes the same angle with the axis 6 as the angle between the axis 6 and the axis 2. A roller thrust bearing I1 is interposed between the drill bit III and the .fitting 3, said bearing including raceways I3 and I3 separated by a series of tapered rollers 26.

- The surface 2| of the lip I3 is parallel withthe surface 22 of the cylindrical portion 4, which is also parallel to the outer surface 23 of the stem I6, thus facilitating assembly of the structure. Two spaced sealing gaskets 26 and 26 are provided in the form of rings embracing the stem I6. The gaskets are kept spaced apart by a ring 23 having a number of perforations 23 therein. Another sealing gasketing ring 3I is provided between the lip I3 and the cylindrical portion 4. The cylindrical portion 4 is provided with a series of openings 33 providing communication from the outside of the drill pipe into the space 34 between the sealing gaskets 26-46 so that the pressure on the outside of the sealinggasket 26 is the same as the pressure on the outside of the sealing gasket 3|.

The bearing chamber between the raceway I8 and the gaskets 3I-26 is devoid of air and filled with oil or grease. This is facilitated by providing plugged openings 35-36 through which lubricant may be first circulated to flush the bearing space free of any air therein and thereafter the space is packed with oil or grease, as by means of an ordinary grease pressure gun.

The bottom of the drill bit is provided with a series of holes or slots 40 through which the circulating fluid or mud within the drill pipe I squirts into the bore adjacent the bit to carry with it the bits of rock and other material chipped away by the drill during the drilling operation, said mud then traveling upward through'the well bore to the top thereof, as is usual.

A ring 42 is threaded on the top of the stem I6 to keep the drill bit from falling of! of the fitting 3 when the drill pipe I is being lowered into or raised from the well.

During the drilling operations the drill pipe I rotates about its axis 2 as a center and turns the offset fitting 3 about the same axis, thus rotating the axis 0f the drill bit Ill about the axis 2. This causes the drill to roll on the bottom of the bore being drilled thereby, the stem I6 turning in the bearing I'I about the axis 6 as the center, while this same bearing is also turning about the axis 2 as a center. At the same time mud is being squirted through the holes 40 with considerable velocity to carry away pieces of chipped rock and other earth matter. Any fluid or mud that may seep past the gasket 25 will reach the space between that gasket and the gasket 26 and will then escape through the holes 29 and 33 to join the upwardly moving stream of fluid in the well.

As previously stated, the bearing I1 is packed with grease or a other suitable incompressible lubricant and is entirely devoid of air. As a result the pressure of the column of mud or other fluid in the bore of the well being drilled cannot force the gaskets 26 and 3I inwardly in the bearing. The pressure of the column of. mud on those gaskets is, however, effective to tend to force the gasket 3I inwardly of the bearing so that the gasket 3I thus maintains the lubricant within the bearing at a pressure substantially equal to the pressure at the bottom of the column of mud in the well. Due to the fact that the mud is being squirted from the pipe I, through the openings 40, into the well there is an appreciable diflerence between the pressure on the inside of the bottom of the drill pipe I. and that of the outside of the bottom of the drill pipe I. The gaskets 26 and 3I which close the two ends of the bearing assembly are both exposed to the hydraulic pressure which prevails on the outside of the bottom of the pipe I and since this pressure is the same on the outer surfaces of both of the gaskets 26 and 3|, there is no tendency for mud to creep past one of those two gaskets, into the bearing, because such creepage would have to be accompanied by a corresponding expulsion of grease through the other gasket. There being no pressure diflerence on the outer sides of the two gaskets 26 and 3I, there is no force available for causing such creepage. There is a pressure difference between the two sides of the gasket 26. which will result in a creepage of the circulating fluid through that gasket. Such creepage will be from the interior of the pipe I, past the gasket 25, to the space 34 between the gaskets 2626. The space 34 on the outside of the gasket 26 is at the same pressure as the space on the outside of the gasket 3| in view of the communication between those spaces by the passageways 29 and 33.

In the embodiment of the invention here illustrated the angle 1 between the axis 6 and a radial line on the cutting surface of the bit II is the complement of the angle a between the axis 5 and the axis 2. As a result of this arrangement the bottom of the bore cut by the bit is fiat. This is not an indispensable feature of the present invention; It is within the purview of the present invention to make the angle between the axis 5 and a radial line on the cutting surface of the bit greater or less than that shown. If that angle is less than what has been illustrated, then the bottom surface of the bore being cut by the bit will be a cone with its apex below the rim. 0n the other hand, if the angle between the axis 6 and a radial line on the conical surface is made greater than that shown, then the shape of the bottom of the hole formed by the bit will be conical, with its apex above its periphery. While the angle between the axis 6 and aradial line on the cutting surface of the drill is shown as less than 90 it may, within the purview of the present invention, be made equal to 90 or greater than 90. If that angle is made equal to 90 then the cutting-surface will be a disc with teeth thereon, rather than a cone with teeth thereon.

In compliance with the requirements of the patent statutes I have here shown and described a preferred embodiment of my invention. It is, however, to be understood that the invention is not limited to the precise construction here shown, the same being merely illustrative of the principles of the invention. What I consider new and desire to secure by Letters Patent is:

bearing between the cutter and the head, gas-- keting means between the head and the cutter on one side of the bearing, gasketing means between the head and the cutter on the opposite side of the bearing whereby both of the gasketing means seal the bearing, and means for equalizing the pressure on the side of each gasketing means outwardly of the bearing;

2. A rotary bit and bearing assembly for earth boring drills comprising a cutter, a rotatable bit head terminating adjacent the cutter, a thrust bearing between the cutter and the head, gasketing means between the head and the cutter on one side of the bearing, gasketing means between the head and the cutter on the opposite side of the bearing whereby both of the gasketing means seal the bearing, and means for equalizing the pressure on the side of each gasketing means outwardly of the bearing, said equalizing means comprising a third gasketing means adjacent to but spaced from one of said first two gasketing means, there being a communicating passageway between said space and the space adjacent the other one of the two first mentioned gasketing means.

3. A rotary bit and bearing assembly for earth boring drills comprising a cutter having an axially extendin stem and a lip around the stem, a rotatable bit head terminating in the space between the lip and the stem, a thrust bearing between the cutter and the head, gasketing means between the head and the stem and gasketing means between the head and the inner wall of ,the lip whereby both of the gasketing means seal the bearing.

4. A rotary bit and bearing assembly for earth boring drills comprising a cutter having an axially extending stem and a lip around the stem, a rotatable bit head terminating in the space between the lip and the stem, a thrust bearing between the cutter and the drill head, gasketing means between the head and the stern, gasketlng means between the head and the lip whereby both of the gasketing means seal the bearing, said cutter having a fluid passageway therethrough maintaining communication from the interior of the headthrough the cutter to the bore formed by the drill, and means for equalizing the pressure on the side of each gasketing means outwardly of the bearing.

5. A rotary bit and bearing assembly for earth boring drills comprising a cutter having an axially extending stem and a lip surrounding the stem, a rotatable bit head terminating in the space between-the lip and the stem, a thrust bearing between the cutter and the head, gasketing means between the head and the stem, gasketing means between the head and the lip, whereby both of the gasketing means seal the bearing, and means for equalizing the pressure on the side of each gasketing means outwardly of the bearing.

6. A rotary bit and bearing assembly for earth boring drills comprising a cutter having an axially extending stem and a lip surrounding the stem, a rotatable bit head terminating in the space between the lip and the stem, a thrust bearing between the cutter and the head, gasketing means between the head and the stem, gasketing means between the head and the lip, whereby both of the gasketing means seal the bearing, and means for equalizing the pressure on the side of each gasketing means outwardly of the bearing, said equalizing means comprising a third gasketing means adjacent to but spaced from one of said first two gasketing means and a communicating passageway between said space and the space adjacent the other one of the first two gasketing means.

7. A rotary bit and bearing assembly for earth boring drills comprising a conical cutter having an axially extending stem and a guiding lip around the stem, a rotatable bit head terminating in the space between the lip and the stem, said cutter being rotatably mounted on the bit head with the axis of the cone at an angle to the axis of rotation of the bit head which is a complement of the angle between the cone axis and an element of the cone, the guiding lip being a frustrum of a cone whose elements projected make an angle with the cutter axis equal to the angl which thecutter axis makes with the axis of rotation of the bit head, a thrust bearing between the cutter andthe head, gasketing means between the head and the stem and gasketing means between the head and the inner wall of the lip whereby both of the gasket-,- ing means seal the bearing.

ALLEN M. ROSSMAN. 

